232 



THE TAPEWORMS 



ally produces the characteristic chain of segments, each of which 

 is known as a proglottid. Obviously the oldest proglottid is the 

 one at the end of the chain, those just back of the neck being 



young and immature. The nervous 

 system, which is developed into a 

 primitive brainlike mass in the scolex, 

 grows forward as two longitudinal 

 nerves which run continuously through 

 all the proglottids in the chain. The 

 muscles and excretory canals also run 

 continuously through the chain. Each 

 proglottid, however, possesses com- 

 plete reproductive systems of both 

 sexes, fully as complex as in the 

 flukes, if not more so (Fig. 83). The 

 female system consists of an ovary, a pair of shell glands (usually 

 spoken of as yolk glands), a seminal receptacle for receiving and 

 holding the sperms until used for fertilization, a vagina for the 



un- 

 or 



Fig. 82. Armed and 

 armed tapeworm ' ' heads 

 sooleces; A, unarmed head of 

 T(Bma saginata; B, armed head 

 of Tcenia solium, x 10. 



t.-- 



gen.pr,- 

 vaq. ' 



Fig. 83. Sexually mature proglottid of beef tapeworm, Tcenia saginata; exc. c, 

 excretory canal; u., nerve cord; ut., uterus; ov., ovary; sh. gl., shell gland, 

 usually called yolk gland; vag., vagina; gen. p., genital pore; sp. d., sperm duct; 

 t., testis. X 7. (Partly after Leuckart.) 



entrance of the sperms, and a uterus for the storage of the mature 

 fertilized eggs. The male system consists of a number of scat- 

 tered testes for production of sperms, all connecting by minute 

 tubes with the sperm duct. The latter, near where it opens at 

 the surface of the body, enlarges into a " cirrus pouch " where 



